Nice Italian town with a cute historic centre. At the end of the harbor there are enough organizations which can offer the same tour for less. Around Bari there are also fun things to do. Just google it.
Interesting Turkish city. In 2020 they will have an EXPO and you can already see that they are trying to patch the city up. The old town (with the Bazaar) is nice to see and there are few landmarks. The city feels more asian (middle eastern) than Istanbul. The people are in general very friendly, but they love to take your money. You need to haggle for everything. Paying 10-15 TL (2,5 TL = 1 EUR) for a 15 minute taxi ride is enough! 50TL for renting a taxi for 2 - 3 hours is also possible, but don't do it at the end of the harbor; it will just cost you a lot of time.
Istanbul is huge and can offer you anything you want. If you are a 1st time visitor, you will probably go to the Haga Sofia, Bazaar, Blue Mosque, Hippodrome and/or Topkapi palace. Well, you are lucky: it is all in the same area (walking distance) and there is a Tram in front of the Cruise-terminal (left and right END) which costs 3 TL per person per trip, bring you to the right area in about 15 minutes. A taxi will be more expensive and will probably take the same time. Buying things at the Bazaar means haggling (except for food); be prepared. Except for the tram, people at the bazaar take Euro's and Dollars at pretty good exchange rates.
What a lovely little city! The trip to the old city is about 45 mintues walking at least! So, try something else! You can rent a scooter for 20 Eur (excluding gas), which is a fun thing to do. You can drive a bit more around. For about 15 KR (about 2 EUR) you can take the bus to the old city centre. Your tour will cost you more. Just be in for a bit of relaxing and nice scenery. If there are more than 1 ships in Dub it will be packed. For a good lunch:go to the side streets! For a good view: go to the mountain up top; but it will cost you. And you can walk on the city walls: also fun.
I think the Croatian people are very kind and know tourism; they live from it! You can be the tourist and don't have to ashamed of it. Just relax and enjoy!